Rarely, and that’s exactly the point. NFL general managers all turn into hyper-secretive, scheming, distrusting, curious horse traders during the draft. In other words, they turn into NFL general managers.

Trade up? Trade back? Stay put?

It’s all possible. And as Detroit Lions GM Martin Mayhew likes to coyly answer when he’s asked every year after the draft if he made any calls or accepted any calls about trading picks, he simply says yes. If he didn’t, he wouldn’t be doing his job. Of course, most times the calls don’t amount to much.

But this year could be different. The Lions are a talented team without a lot of gaping holes on their roster. They have a new coach who has said he expects to win and win big right away. That means the addition of an elite player who makes an impact right away. And that means the Lions would have to trade up from the No. 10 overall pick in tonight’s first round to land that player.

Most reports and rumors concerning the Lions trading up have focused on their trying to land Clemson receiver Sammy Watkins. The rumors have been that the Lions could try to trade up to No. 3 with Jacksonville, No. 4 with Cleveland or No. 5 with Oakland.

“Certainly, he would be an impact pick for them, and when they would line up on offense they would have a dynamic group with a terrific quarterback,” said former Washington Redskins and Houston Texans GM Charley Casserly, now an NFL Network analyst. “The thing you have to weigh is how many other needs you have, what it’s going to cost to do it, and you still haven’t solved your secondary.

“I mean, you’re getting a Pro Bowl player and you’re putting yourself in a position where you’re hard to defend and there is not a Pro Bowl corner at 10. So in a sense, you’ll be picking up a corner (at No. 10) better than you have, but there’s a little bit of a reach there.”

Jimmy Johnson and the Dallas Cowboys came up with the draft-trade value chart in the early 1990s to assign point values to each pick in the draft, thereby creating a rough but simple mathematical formula and one that states that the Lions might have to give Jacksonville next year’s first-round pick to move to No. 3 this year. Or second- and third-rounders to move up to No. 4 or No. 5.

But no two trade value charts are the same. Every team has its own version. Market forces on draft day also help determine negotiating power — as well as a team’s philosophy.

“I typically don’t value receivers that highly that you would trade up,” said former Indianapolis GM Bill Polian, now an ESPN analyst, “particularly when you’ve got Megatron and the kid that came over from Seattle (Golden Tate). They can get a receiver without trading up, is my point, if that’s the position they want.”

This will be coach Jim Caldwell’s first draft with the Lions. But Polian worked him as the head coach of the Colts, and Polian said Caldwell did not place an inordinately high value on receivers.

Polian also thinks the receivers behind Watkins aren’t that far behind him in terms of quality.

“Can you get as good a receiver at 10 as you can get at 4, let’s say?” Polian said. “My answer is usually yes.”

Gil Brandt, a former vice president of player personnel for Dallas, thinks there’s too much depth later in the draft to sacrifice a lot for one player.

“I would imagine that the price will be high because everybody is trying to get somebody,” said Brandt, an NFL Network analyst. “And in imagining that the price is high I don’t think that teams are willing to give up a lot because they know if they give up a second and third, they’re losing more because there are much better players in the second and third round than there was a year ago.”

Though almost no one sees an imminent trade coming for the Lions, Casserly summed up what could very well be the Lions’ thinking.

“I guess that if you’re looking at who you’re going to get at 10 and what else you’re giving up, if it’s next year’s (first-rounder), then it’s not even a consideration,” he said. “You have to assume you’re giving up a (second-rounder). And I think in this year’s draft I want to hold my picks because I think there’s a number of good players.”